This invention relates to a process for making strong, tough, high gloss, transparent, uniform, substantially amorphous films from ordered poly(ether ketone ketones) sometimes referred to hereinafter as PEKKs.
PEKKs are well known and are described, i.a., in U.S. Pat. No. 3,065,205 (Bonner); U.S. Pat. No. 3,441,538, (Marks), U.S. Pat. No. 3,442,857 (Thornton), and U.S. Pat. No. 3,516,966 (Berr). PEKK films and a melt-casting process for making PEKK films are described in detail in U.S. Pat. No. 3,637,592 (Berr) and British Patent 1,340,710 (Angelo).
The PEKK principally employed in melt-casting films according to the above art was a copolymer of terephthalyl chloride (T), isophthalyl chloride (I), and diphenyl ether (DPE). The polymer, made by a one-step process was characterized by an essentially random distribution of the T and I groups along the chain backbone.
More recently, U.S. Pat. No. 4,816,556 (Gay et al.) described a two-step ynthesis of PEKK resin characterized by an ordered (nonrandom) distribution of T and I groups along the chain backbone. In these PEKKs, the T and I groups either alternate or are in blocks, and the resins are described as ordered polyetherketones. The first step in that process is an oligomerization step in which either only the T or only the I comonomer react: with DPE to form an oligomeric structure -DPE-T-DPE- or -DPE-I-DPE-. In the second step, this oligomeric intermediate is contacted with further T and I to form the final product. These ordered PEKKs have a higher heat of fusion, a smaller difference between the melting temperature and the temperature of onset of crystallization, and a melting temperature greater than the melting temperature of PEKKs having the same gross composition wherein the repeat units occur in random sequence. These ordered PEKKs are more suitable in manufacturing lecause of their better melt processing characteristics than their random counterparts.
Both Berr (U.S. Pat. No. 3,637,592) and Angelo (British Patent 1,340,710) describe a process for making films from random PEKK by continuous extrusion and melt casting of PEKK resin onto a quench (or, casting) drum. In order to obtain amorphous film, both Berr and Angelo consider it necessary to cool the casting drum to or below room temperature.
However, when a thin film of ordered PEKK resin of Gay et al. is cast onto a drum cooled to below about 100.degree. C., especially below 80.degree. C., it buckles and cannot be laid down smoothly upon the drum, this effect being more severe at progressively lower temperatures. Yet, smooth lay-down is required for producing uniform film. In the absence of smooth lay-down, ridges, large bumps, and waviness occur in the film. In addition to its other shortcomings, the three-dimensional character of the resulting film renders wind-up of a good quality film package or roll virtually impossible in ordinary film winding equipment.
It, therefore is desirable to provide a process for melt casting ordered PEKK resins into a smooth, essentially two-dimensional, high quality film or sheet.